Over the last week I also had a look at some of the Unity 5 physics bugs I mentioned in an earlier post.

It turns out the rigidbody freezing bug only happens when I modify a rigidbody’s mass properties (i.e. mass, inertia tensor etc.)  I was quite easily able to repro this in a very simple project, so I’ll send this off to Unity when I get a chance.

After browsing the Unity forums I found out that hinge joint motors not working is caused by the motor not waking up the rigidbody.  As a temporary solution, if you force the rigidbody to wake up every update, the motor works.  I also found I had to multiply my torque values by a factor of around 50 to get similar behaviour to that in Unity 4.6.

Velocity drives definitely aren’t working for me.  Again, I was able to repro this in a very simple project.  One for another bug report.

I haven’t had a chance yet to look at the hinge joint limit and OnCollisionExit issues, but I’ll keep chipping away at these next week.  I also noticed that my gears don’t seem to be working properly, sometimes the gears (particularly rack gears) get stuck.  I checked and the configurable joints I’m using for the gear constraints do still seem to be updated correctly, so I’m not sure what’s changed here.  I always was concerned I’d find some slightly different behaviour in Unity 5 with PhysX 3.3 that would unavoidably break the delicately tuned physics setup in my game, and this may be evidence of that.  Let’s hope not, more investigation required!